The present invention relates generally to the field of orthodontics, and more particularly to a system and method for detecting positional differences between different models of a patient's teeth, as well as deviations from a planned course of treatment to gradually reposition teeth.
An objective of orthodontics is to move a patient's teeth to positions where function and/or aesthetics are optimized. Traditionally, appliances such as braces are applied to the patient's teeth by an orthodontist or dentist and the set of braces exerts continual force on the teeth and gradually urges them toward their intended positions. Over time and with a series of clinical visits and adjustments to the braces, the orthodontist adjusts the appliances to move the teeth toward their final destination.
More recently, alternatives to conventional orthodontic treatment with traditional affixed appliances (e.g., braces) have become available. For example, systems including a series of preformed aligners have become commercially available from Align Technology, Inc., Santa Clara, Calif., under the tradename Invisalign® System. The Invisalign® System includes designing and/or fabricating multiple, and sometimes all, of the aligners to be worn by the patient before the aligners are administered to the patient and used to reposition the teeth (e.g., at the outset of treatment). Often, designing and planning a customized treatment for a patient makes use of computer-based 3-dimensional planning/design tools. The design of the aligners can rely on computer modeling of a series of planned successive tooth arrangements, and the individual aligners are designed to be worn over the teeth and elastically reposition the teeth to each of the planned tooth arrangements.
While patient treatment and tooth movements can be planned prospectively, in some cases orthodontic treatment can deviate from the planned treatment or stages. Deviations can arise for numerous reasons, and can include biological variations, poor patient compliance, and/or factors related to biomechanical design. In the case of aligners, continued treatment with previously designed and/or fabricated aligners can be difficult or impossible where a patient's teeth deviate substantially from the planned treatment course. For example, subsequent aligners may no longer fit the patient's teeth once treatment progression has deviated from the planned course.
Because detecting a deviation from planned treatment most typically relies on visual inspection of the patient's teeth or observation of appliances no longer fitting, treatment can sometimes progress significantly off track by the time a deviation is detected, thereby making any required corrective measures more difficult and/or substantial. Earlier and better off track determinations would, therefore, be beneficial in order to recalibrate the fit of the aligner device on the teeth. Accordingly, improved methods and techniques of detecting and correcting treatment that has deviated from planned or desired treatment course would be desirable, particularly methods allowing early detection of treatment deviation.